Method of and device for controlling electric arcs



D. F. COMSTOCK.

METHOD OF AND DEViGE FOR CONTROLLING ELECTRIC ARCS.

APPLICATION FILED OCT-20,1915.

Patented Feb. 1, 1921.

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. UNITED STATES;

PATENT OFFICE.

DANIEL F. COMSTOCK, OF BROOKLINE, MASSACHUSETTS, ASSIGNOR, BY MESNE nssxcmnmrrs, T0 'rncnmoonon MOTION PICTURE CORPORATION, OF BOSTON,

MASSACHUSETTS, CORPORATION OF MAINE.

METHOD OF AND DEVICE FOR C ONTROTQLING'ELECTRIC ARCS.

Specification of Letters Patent.

Patented Feb. 1, 1921.

7 Application filed 0ctober 20, 1915, Serial No. 56,994. I

To all whom it may emwem:

Be it known that I, I)ANIEL F. CoMs'rooK, a citizen of the United States, and resident of Erookline in the county of Norfolk and State of Massachusetts, have invented new and useful Im rovements in Methods of and Devices for ontrolling Electric Arcs, of which the following is a specification.

My invention relates to electric arcs, and in one embodiment to electric arcs adapted to maintain an intense source of light in a constant axis. One object of my invention is to enable an are carrying a heavy current to be used as the source of illumination in a projection apparatus requiring intense illumination, my invention including provisions for maintaining the are within a predetermined space between and in a constant relation to the electrodes between which it is struck.

Further objects of myinvention are to provide a method of control for electric arcs with respect to the prevention of flamtil ing, blowing, wandering, vibration, hissing and singing, as well as to provide devices for the regulation and control of the position with respect to the electrodes of an are light which shall be adapted to maintain the brightest portions of the light emitting area in the same position with respect to the con densing lenses or reflectors of optical apparatus, for instance such as a search light or a rojection lantern.

:or the above and other purposes my invention comprises a method of controlling the flow of the-ionlzed stream between separated electrodes and under heavy currents, I

and apparatus for practising my method.

'ltrc lamps of theprior art, for instance focussing lamps intended foruse with elements of an optical system in which an in tense source of llluminatlon maintained in a relatively constant position with respect to the optical surfaces is a necessity, have heretofore been rendered unsatis .actory,

.whenever the current value is increased beyond a critical figure, by several well-known phenomena. The positive or crater bearing carbon, which in general use is larger than the negative or cathode carbon, as is well huovui, presents at its surface the most bril liant illuminatedarea of the entire source not light, the glowing carbon. on this side of the air-gap constitutuig the arc havuig a .usually employed,

higher specific emission than any other part of either the ionized stream constituting the are proper or the remainder of the anode and cathode surfaces. When, as compared with the relative size of the carbon electrodes current density increases, the flow of the arc between the anode and cathode carbons becomes more and more disturbed. 'It is a frequent occurrence that the spot'of greatest illumination on the surface of the positive carbon wanders about the crater. 'lhe arc itself ex ands and flames, sometimes explosively.

the arc withinthe space between the electrodes sometimes becomes violent, and singing, hissing and flaming arcs are familiar to those skilled in the art as consequences of increasing the current. a

For the projection purposes forming one intended use of my invention an arc struck between electrodes situated with relation to one another at an angledifi'ering consider he "vibration of ably from a straight angle, for instance at a right angle, has the'advantage of exposing the area of most intense illumination to an optical axis arranged in the longitudinal axis of the positive carbon, thus permitting the positive carbon to be fed up as it is consumed without altering the position in space of the intensely illuminated area. The effect of flaming, vibration, blowing and wandering of the are under a heavy current is, however, much increased by striking the are between the electrodes at f I will now describe one form.

such an angle. of device and indicate the method by which have succeeded in overcoming the difficulties incident to a relatively heavy current, for instance of the order of 100 amperes, or the angular position of the electrodes, or both..

In the accompanying drawing,

The single figure is a side elevation in section showing the electrical circuits in diagram.

The electrodes or carbons l and 2 may be supported in any desired manner, but I pro fer to mount the positive electrode 2 for longitudinal, movement in an insulating sleeve 3 of alundum or other highly refractory material fast in a hole in the pole piece N ofmember 5 of an iron magnetic circult frame 5, 6, 7 also constituting the mocha-iii cal support of the carbons it and t, and, if

lltlti tut desired, of any known or suitable regulat upon the optical axis a: of the optical system, when the light is employed for projection urposes.

Po e piece N preferably is so designed as to leave a greater mass and surface above than below the carbon 2, and the surface of pole-piece S is preferably sloped or curved to lie roughly parallel to the bisector of the an le between the electrodes.

11 exciting coil C is wound on any suitable part of frame 5, 6, 7, for instance 011 the connectin -piece 6.

When coil is energized, a magnetic field existsin the dielectric between the pole pieces N and Sin which equal lines of force may be conceived of as defining an envelop or capsule having striae, surfaces or closed layers substantially central upon an areuate axis 3 at substantially the desired direction and position for the central axis of the areproper, the magnetic direction everywhere lying substantially parallel to the arc and completely surrounding the area of possible flow of current or charged particles in passage between the carbons.

It is well known that the flow of such an are or stream is susceptible of being stopped or distorted by a magnet, the are tending strongly to follow the lines of force even when opposed to a current flow directed by the posltion of the electrodes and the shortest path through the surrounding dielectric. I have determined by experiment that this efiect may be utilized as described not to distort or blow out the are, but instead to maintain the arc in its proper position, a magnetic field positioned as described virtually constituting a closed tube in which the arc is directed and confined against the relatively feeble forces tending to cause wandering, blowing and vibration. Change in the mass, distribution of mass, or relative position of the pole pieces then aifects the position of the arc in the space between and with respect to the surfaces of the electrodes, and

by arranging the relation of these constants the brightest spot and the are proper may be adjusted and maintained in adjustment with certainty. I have shown, for instance, a pole piece N having an eccentric fixed mass 8 above the anode carbon, but it will be obvious that the mass and position of either pole piece may be made changeable by providing adjustable or removable parts, if desired.

The degree to which the inherent self destructive and disquieting tendencies of the are, which increase with the current flow, are resisted by a longitudinal magnetic field surrounding the are as described increases with the intensity of the field. I may therefore arrange for energizing the coil C by a current related to the current flowing in the are.

As shown in the figure, one arrangement of circuits comprises coil C connected in a shunt circuit 10, containing if desired a variable resistance 1', the circuit 10 being in parallel with the arc [and if desired, a series resistance R] with respect to the current leads from the source of energy D.

What I claim is:

1. Electrical apparatus comprising electrodes angularly arranged with a gap therebetween, and magnetic pole pieces disposed at opposite ends of the gap so as to direct a magnetic field longitudinally of the gap, one pole piece being displaced outwardly from the smaller angle between the electrodes with respect to the center of the associated electrode.

2. Electrical apparatus comprising electrodes angularly arranged with a gap therebetween, and magnetic pole pieces respectively surrounding the electrodes with their ends disposed near the opposite ends of the electrode gap, one of the pole pieces having its axis displaced outwardly from the smaller angle between the electrodes with respect to the axis of the associated electrode.

3. A supporting frame for an arc lamp comprising a rigid frame of magnetic mate rial terminating in pole pieces, each bored to carry one of the electrodes of the lamp, one of said pole-pieces being out of line with the bore in the other, and having a terminal surface lying substantially in the direction of the bisector of the angle between the bores.

Signed by me at Boston, Massachusetts, this nineteenth day of October, 1915.

DANIEL F. COMSTO OK. 

